Theimddynamically Stable Metal / III-V Compound-Semiconductor Interfaces

1985 ◽  
Vol 54 ◽  
Author(s):  
R. Stanley Williams ◽  
Jeffrey R. Lince ◽  
Thomas C. Tsai ◽  
John H. Pugh
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Compound Semiconductor ◽  
Enthalpy Change ◽  
Reaction Products ◽  
Bulk Materials ◽  
Semiconductor Interface ◽  
Group V ◽  
Semiconductor Interfaces ◽  
Higher Temperature

ABSTRACTChemical reactions that occur at a metal/III-V compound-semiconductor interface should be minimized if the change in Gibbs free energy of the bulk materials with respect to any possible reaction products is positive. However, the large positive change in entropy caused by vaporization of the highly volatile group V elements is a very important contribution to the Gibbs free energy of these systems, especially at higher temperatures. Thus, a particular metal/III-V compound-semiconductor interface may be thermody-namically stable at one temperature, but unstable with respect to sublimation of elemental group V species at a higher temperature if the enthalpy change for the reaction is positive. Examination of bulk phase diagrams makes it possible to rationalize the reaction products observed and to predict which will be the most stable interface for any particular metal/III-V system.

scholarly journals The Reaction Thermodynamics during Plating Al on Graphene Process

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 330 ◽  
Author(s):  
Zhanyong Zhao ◽  
Peikang Bai ◽  
Liang Li ◽  
Jing Li ◽  
Liyun Wu ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Chemical Reduction ◽  
Enthalpy Change ◽  
Reaction Process ◽  
Endothermic Reaction ◽  
Graphene Surface ◽  
Second Stage ◽  
Reaction Thermodynamics ◽  
Two Stages

This research explored a novel chemical reduction of organic aluminum for plating Al on a graphene surface. The thermodynamics of the Al plating reaction process were studied. The Al plating process consisted of two stages: the first was to prepare (C2H5)3Al. In this reaction, the ΔH(enthalpy) was 10.64 kcal/mol, the ΔG(Gibbs free energy) was 19.87 kcal/mol and the ΔS(entropy) was 30.9 cal/(mol·K); this was an endothermic reaction. In the second stage, the (C2H5)3Al decomposed into Al atoms, which were gradually deposited on the surface of the graphene and the Al plating formed. At 298.15 K, the ΔH was −20.21 kcal/mol, the ΔG was −54.822 kcal/mol, the ΔS was 116.08 cal/(mol·K) and the enthalpy change was negative, thus indicating an endothermic reaction.

scholarly journals Thermodynamic insight into the growth of nanoscale inclusion of Al-deoxidation in Fe–O–Al melt

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hong Lei ◽  
Yuanyou Xiao ◽  
Guocheng Wang ◽  
Hongwei Zhang ◽  
Wei Jin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Liquid Iron ◽  
Reaction Products ◽  
Straight Line ◽  
Nano Alumina ◽  
Increasing Temperature ◽  
The Relationship ◽  
Insight Into

Abstract Products of Al-deoxidation reaction in iron melt are the most common inclusions and play an important effect on steel performance. Understanding the thermodynamics on nano-alumina (or nano-hercynite) is very critical to explore the relationship between Al-deoxidation reaction and products growth in iron melt. In present study, a thermodynamic modeling of nano-alumina inclusions in Fe–O–Al melt has been developed. The thermodynamic results show that the Gibbs free energy changes for the formation of nano-Al2O3 and nano-FeAl2O4 decrease with the increasing size and increase with the increasing temperature. The Gibbs free energy changes for transformation of nano-Al2O3 into bulk-Al2O3 increase with the increasing size and temperature. The thermodynamic curve of nano-alumina (or nano-hercynite) and the equilibrium curve of bulk-alumina (or bulk-hercynite) obtained in this work are agree with the published experimental data of Al-deoxidation equilibria in liquid iron. In addition, the thermodynamic coexisting points about Al2O3 and FeAl2O4 in liquid iron are in a straight line and coincide with the various previous data. It suggested that these scattered experimental data maybe in the different thermodynamic state of Al-deoxidized liquid iron and the reaction products for most of the previous Al-deoxidation experiments are nano-alumina (or nano-hercynite).

Reaction Mechanism of an Al-TiO2 System

2010 ◽  
Vol 97-101 ◽  
pp. 1624-1627 ◽  
Author(s):  
He Guo Zhu ◽  
Jing Min ◽  
Ying Lu Ai ◽  
Qiang Wu
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Heating Rate ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Volume Fraction ◽  
Reaction System ◽  
Exothermic Peak ◽  
Higher Temperature ◽  
Α Al2o3

The reaction mechanism of an Al-TiO2 system is discussed. Thermodynamic analysis indicates that the reaction between Al and TiO2 can occur spontaneously due to the negative Gibbs free energy of the Al-TiO2 reaction system. When the reinforcement volume fraction is 30%, there is an endothermic peak and an exothermic peak in the DSC curve. But when the reinforcement volume fraction increases to 100%, there are two independent exothermic peaks and the height of them increases obviously. With increasing the heating rate, the ignite temperature becomes higher and all the peaks move to the higher temperature direction. The reactions between Al and TiO2 consist of two steps: first, Al reacts with TiO2 to form the stable α-Al2O3 particles and the active Ti atoms; second, the active Ti atoms react with Al to form Al3Ti.

Alloying and entropy effects in predicting metal/compound–semiconductor interface reactivity

1987 ◽  
Vol 2 (4) ◽  
pp. 516-523 ◽  
Author(s):  
John F. McGilp
Keyword(s):  
Solid State ◽  
Thermodynamic Model ◽  
Compound Semiconductor ◽  
Solid State Reactions ◽  
Metal Compound ◽  
Alloy Formation ◽  
Semiconductor Interface ◽  
Group V ◽  
Specific Effects ◽  
Entropy Effects

A previous bulk thermodynamic model, which used enthalpies of compound and alloy formation to predict metal/compound–semiconductor interface reactivity, is extended to include entropy. It is shown that, for most metals on CdTe, GaAs, GaSe, InP, and MoS2, solid-state reactions are energetically favored up to semiconductor dissociation temperatures and, consequently, entropy effects are minimal. Gold and silver, with their small enthalpies of metal–semiconductor anion compound formation, can be exceptions. Even here, the results for gold/III–V systems favor solid-state reaction at room temperature, but at higher temperatures entropy drives the reaction via vapor-phase production of the group V element. The binary phase bulk thermodynamic model is not sufficient to predict absolute reactivity, but can rank the reactivity of the various metal–semiconductor combinations successfully, as long as possible alloy formation is included. It is suggested that the limitations of the model are due to the specific effects of the interface.

scholarly journals Theoretical investigations on the phase transition of pure and Li-doped AlH3

RSC Advances ◽  
2017 ◽  
Vol 7 (67) ◽  
pp. 42024-42029 ◽  
Author(s):  
Zheng Mei ◽  
Feng-Qi Zhao ◽  
Si-Yu Xu ◽  
Xue-Hai Ju
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Aluminum Hydride ◽  
Enthalpy Change ◽  
Free Energy Change ◽  
Gibbs Free Energy Change ◽  
Α Phase ◽  
Theoretical Investigations

The calculated Gibbs free energy change and enthalpy change for the γ → α phase transition and heat capacity indicate that the aluminum hydride synthesized in experiments is Li-doped.

Study on the Reaction Mechanism of (α-Al2O3+TiB2+TiC)/Al Composites Fabricated by Al-TiO2-B4C System

2010 ◽  
Vol 150-151 ◽  
pp. 84-87
Author(s):  
He Guo Zhu ◽  
Jin Min ◽  
Da Chu ◽  
Huan Wang
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Reaction System ◽  
Higher Temperature

The composites (-Al2O3+TiB2+TiC)/Al has been fabricated by using exothermic dispersion synthesis. Thermodynamic analysis indicated that the reaction between the Al and TiO2 can spontaneously occur due to the negative Gibbs free energy of the Al-TiO2 reaction system. With the increase of B4C/TiO2 mole ratios, the exothermic peaks increase move to the higher temperature and the corresponding ignite temperatures also increase. The reaction results indicate that when the B4C/TiO2＝0, the reinforcements are composed of -Al2O3, Al3Ti, with the increase of B4C/TiO2, the amount of Al3Ti decreases and the TiC and TiB2 form simultaneously. When the B4C/TiO2 increases to 1/3, the Al3Ti almost disappear and the reinforcements of the composites are consisted of -Al2O3, TiC and TiB2.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

Sign in / Sign up

Export Citation Format

Share Document